Hydraulic valves for cam phasers for internal combustion engines are well known in the art. The hydraulic valve includes a piston that is axially movable in a housing of the hydraulic valve and that controls a hydraulic loading of the cam phaser. Hydraulic valves come in many different configurations. The housing is configured hollow cylindrical. The piston is also configured hollow cylindrical. Controlling the cam phaser is done hydraulically by positioning the flowable piston and opening and closing connections configured in the housing accordingly.
The publication documents DE 10 2013 104 573 A1 and DE 10 2013 104 575 A1 disclose a hydraulic valve which includes a supply connection at a housing end so that direct flowing of the piston received in the housing and thus straight loading of the piston with a hydraulic fluid that is fed through the supply connection can be provided. The piston has a complex outer geometry so that pressure forces are balanced to minimize pressure effect on the piston position.
The publication documents US 2014/0311333 A1 and US 2014/0311594 A1 disclose a hydraulic valve which includes check valves that are configured at a circumference of the piston. This either requires a complex housing configuration for receiving and securing the check valves or the housing is configured in plural components and requires a high level of assembly complexity. The piston is configured from multiple components and the individual components are joined concentrically which requires complex assembly since axial misalignments have to be avoided when the components are pressed together.
Another hydraulic valve which includes so called center position locking can be derived from the publication document EP 2 966 272 A2. The piston has a complex external geometry since additional locking connections are arranged in the housing of the hydraulic valve.
Another hydraulic valve which includes a particular piston for a hydraulic valve for a cam phaser may be found in Patent Application US 2017/0260882 A1 filed on Nov. 26, 2016, which is incorporated herein in its entirety. This hydraulic valve also invented by the inventor of this application has many common features of the present invention.